1. Field of the Invention
The present invention relates to an arrow shaft, and in particular, to an arrow shaft including a straightness marking.
2. Description of the Related Art
An arrow shaft is classified with a variety of materials and types, but recently, arrow shafts using carbon fibers have become more mainstream.
In general, such an arrow shaft is manufactured via cutting of a carbon prepreg treated sheet, laminating and winding, taping, heat treatment and cooling, core removing, and grinding.
Ideally, the arrow shaft manufactured as above should have a true straightness. However, some arrow shafts actually do not retain a true straightness, and therefore, at least a portion of the arrow shaft has a curved shape.
Korean Patent Laid-Open Publication No. 10-2011-0042436, Korean Utility Model Registration No. 20-0232099, U.S. Pat. No. 4,155,172, and U.S. Pat. No. 5,533,272 disclose methods for measuring a straightness of a manufactured arrow shaft, and U.S. Patent Laid-Open Publication No. US2012/0165141 A1 proposes a method for improving a straightness of a manufactured arrow shaft.
As shown in FIG. 2, the straightness of such an arrow shaft is defined by a numerical value converted from the distance between a virtual axial center line (BL) of an arrow shaft having ideally a straight shape, and an actual axial center line (CL) of an arrow shaft to be measured.
For example, the numerical value for the straightness of an arrow shaft 101 may be indicated by ±0.0025 inch, and such a numerical value may be printed on the package of a six-pack or a twelve-pack of arrow shafts for sale. A numerical value for the straightness to be printed on the package of arrow shafts is generally the maximum value. The lower (absolute) value of straightness means an ideal straight line. An arrow shaft having lower values of straightness becomes more expensive.
In the case of users using various arrows for hunting and game, users may mount two to five sheets of fletching on the outer circumferential surface of the arrow shaft. Korean Patent Laid-Open Publication No. 10-2008-0082878, entitled “SHAFT OF AN ARROW,” discloses a technique wherein fletching indication patterns are previously provided on the arrow shaft to allow for more accurate mounting of the fletching. However, in case of above Korean Patent Laid-Open Publication No. 10-2008-0082878, fletching patterns are simply marked as radially spaced apart from each other similar angles along the circumferential surface, and thus it is not possible to compensate for errors in the straightness of the arrow shaft at all.
That is, as described above with reference to FIG. 2, an arrow shaft inevitably has a value of straightness corresponding to the value of an error being deviated from an ideal value of straightness. The higher value of straightness (i.e., the “value of an error” or “error of straightness”) gives adverse effects on the flight performance and accuracy of the arrow.